Data collected by a probe car has been used in searching a recommended route for a vehicle when it travels on a road. The probe car is a vehicle that includes on-board various devices such as various sensors and a communication device, collects data such as vehicle location, travel speed, travel distance, route information (hereafter, referred to as “probe data”) and transmits the collected probe data to a predetermined server. In many cases, the probe car used is a commercial vehicle such as a taxi or a truck, or a private car. In recent years, it has become possible to collect probe data by executing an application programmed to collect probe data with a multi-functional mobile phone (smartphone) and transmit the collected probe data to a server.
On the other hand, a route search technology for providing an optimal route to a destination is a basic function of a navigation device. Such a technology commonly uses a method of calculating a route along which the amount of time required or traveling distance from the departure point to the destination is minimal. However, such a recommended route may include a road that is not used by the local people, such as a narrow road or a road having poor visibility. This causes a desire for a route that is selected taking into consideration not only time and distance but also comfort and safety.
Patent literature 1 discloses a method of executing a route search by detecting a crossing, at which many vehicles branch off, as a main branching node, based on a plurality of pieces of travel history data obtained from the probe data, preparing a probe section having the main branch node as an ending point, and executing a route search using this probe section. According to the teaching of the Patent literature 1, constructing road links based on the driver's actual travel records naturally results in selecting a series of road links that follow any road link, along which the driver has traveled, as a recommended route, and thus enables preparing and providing a recommended route which reflects the know-how concerning route selection by the driver who has traveled similar road areas.
Patent literature 2 discloses a technology for searching a route, which involves classifying a plurality of pieces of travel history data obtained from probe data by categories including driver information, vehicle information, purpose of travel, setting a link cost by calculating, by category, ratios of links along which travels are made assuming that a plurality of pieces of travel history data classified into the same category are treated as the pieces of the travel history data relative to drivers having the same liking in route selection, and searching a route with placing priority to the link along which the drivers having the same liking have traveled. Patent literature 2 states that a driver uses the route selection know-how of other drivers who have the same purpose or liking as that of the driver, he can get a route which is created in consideration of his liking.